“Most boycotts work slowly or don’t work at all. This one has been very effective,” Glickman said. (DOMINICK REUTER/AFP/Getty Images)

It was only a day-long boycott, but it aimed for long-lasting effects.

The Thursday boycott of Amazon, Apple and FedEx over their links to the National Rifle Association was urged by students of the high school in Parkland, Fla., where 17 victims died in a mass shooting Feb. 14.

Experts said we may never know how much the 24-hour campaign actually dented sales, but it demonstrated the companies' brands aren't bulletproof.

"I won't be surprised if they soon make the calculation they want to take a stance. Companies want to have brands they're proud of, that are not sullied or contaminated by something considered unpopular," Lawrence Glickman, an expert in boycotts at Cornell University, told the Daily News.

He highlighted the fact boycott threats have already pushed bellwether companies such as MetLife, United, Delta, Enterprise and Hertz to end their deals with the NRA.

"Most boycotts work slowly or don't work at all. This one has been very effective," Glickman said.